With the continuous development and progress of semiconductor techniques, the integration of ICs is increasing and the sizes of various devices are shrinking for the applications of Ultra Large Scale Integrated (ULSI) circuits. The distances among the devices have become smaller and smaller so that a chip could accommodate more devices to be formed thereon. In device integration of semiconductor manufacture, the key point of is the capability of lithography. In general, the lithography technique is used to transfer the desired patterns from the reticles or masks to the substrate for defining the determined circuits.
Typically, the photo-sensitive material, such as photoresist, is first deposited on the semiconductor substrate in the procedure of transfering patterns onto substrate. Then an illumination is performed to irradiate the photo-sensitive material through the reticles or masks and to expose the photo-sensitive material with the patterns thereof. Therefore, the patterns of the reticles or masks can be transferred and defined onto the photoresist. After performing the development process, the patterns formed on the photoresist are the same as that of the reticles or masks. Thereafter, the photoresist serving as a mask is used to perform the required etching step, doping procedure, etc. The residual photoresist is removed after performing the required procedures.
Referring to FIG. 1, a side elevation view is used to illustrate the chamber 10 of a Gasonics L3510 (trademark) etcher. An input tube 15 is connected to the chamber 10 for inputting the reactive gases, such as O.sub.2 and N.sub.2, into the chamber 10. An electrode plate 20 is mounted on the bottom of the chamber 10 to load a wafer 25. The load is for performing an ion bombardment process removing photoresist formed on the wafer. A microwave is used to activate the reactive gases to form the oxygen plasma particles comprising of O.sup.+, O.sub.2.sup.+, O.sub.2, O.sub.2.sup.-, and O during the removing procedure. The above plasma particles are used to remove the photoresist by colliding with photoresist on the wafer 25.
It is noted that the operation temperature for performing the etching step by using the Gasonics L3510 (trademark) etcher is about more than 200 degrees centigrade. For adjusting the operating temperature to be the required value, a heater 30 is connected to the bottom of the electrode plate 20 to heat up the wafer 25 through the electrode plate 20. The heater 30 is electrically connected to the power supply (not shown in FIG. 1) outside of the chamber 10 through the electric wire 40. However, because the chamber 10 must be maintain under a vacuum condition for removing the photoresist with a dry etching step, all channels connected into the chamber 10 must be covered with sealing means for preventing leakage. Therefore, the heater 30 and the electric wire 40 thereof are bundled with a heater adapter flange 50 in order to maintain the vacuum condition of the chamber 10.
Referring to FIG. 2, the heater adapter flange 50 described above is shown. In general, the material of the heater adapter flange 50, such as Teflon (trademark; butafluoroethylene polymer), is refractory and with lower hardness for effectively sealing the heater 30 and the electric wire 40. The heater adapter flange 50 comprises a duct portion 70 and a cylinder portion 75 connected to the end of the duct portion 70. A central opening 120 is formed on the top surface of the cylinder portion 75 and penetrates through the cylinder portion 75 and the duct portion 70. Additionally, six screw holes 110 are formed on the top surface of the cylinder portion 75 around the central opening 120 and penetrate through the cylinder portion 75. When the heater adapter flange 50 is used to seal the heater and the electric wire, a small O-ring 80 and a big O-ring 90 are used to enhance the sealing efficiency between the heater and the heater adapter flange 50 and between the heater adapter flange 50 and the chamber, respectively. Then, to fix and mount the heater adapter flange 50 onto the chamber 10 for sealing, six screws are turned into the six screw holes 110.
It is noted that the top surface 100 of the cylinder portion 75 is usually distorted out of shape after being fastened with the six screws to fix and mount the heater adapter flange. This distortion occurrs because the heater adapter flange has a hardness lower than that of the metal screws. Moreover, in the central opening 120, the distorted cylinder portion 75 is also the reason why the small O-ring 80 cannot effectively seal the chamber. On the other hand, the unequal screwing degrees for the six screws is also a reason why the big O-ring 90 cannot effectively seal the chamber 10.